A straight metal rod with a shank at one end to fit the drilling machine chuck, and the opposite end externally threaded or tapered to receive a detachable bit. The rod has a passageway throughout its entire length for conducting air or water to clear the hole being drilled. Overall length must be at least 15 inches (381 mm). Excludes drill rods designed for core drilling. See also DRILL ROD SECTION, ROCK DRILL; and SHANK, ROD, ROCK DRILL.